Induction clutch



March 4, 1958 w. H. BOWES 2825829 INDUCTION cr.uwca

Filed Ost. 2, 1956 v 4 Shets-Sheet 5 March 4, 1958 w. H. BOWES 2825,829

INDUCTION CLUTCH Filed Ost. 2,1956 4 Sheets-Sheet 4 Bv MW/6W UnitedStates Patent Ofi ice 2,825829 Patented Max. 4, 1958 INDUCTION CLUTCI-IWilliam H. Bowes, Peterborough, Ontario, Canada, as-

signor to Canadian Patents and Development Limited, Ottawa, Ontario,Canada, a company Application Ocioher 2, 1956, Serial N0. 613,450

18 Claims. (Cl. 310-102) The invention relates to an induction clutch cfparticular advantage in marine use but which is also useful for suchpurposes as rolling mill drives, locomotive drives, or in an autom-obiletransmission. An important feature of the inVentin is that the inductionclutch can be designed so that the drive through the cluteh isreversible.

Prioi' to the present invention a satisfacto1y clutch and reversingmechanisrn has nOt been available as a single unit for use in largeships. The mechanisms presently used for coupling between the sourcepower and the propeller of the ship depend upon the type of source cfpower which is usually one of three kindssteam turbine,turbine-electric, er diesel engine.

The steam turbine is a high speed source cf p0wer and in the past hashad a fixed coupling through suitable reduction gears to the W speedpropeller shaft. Reversing of the ropeller shaft has been accomplishedby shutting off the steam supply to the turbine and diverting the stean1to a second smaller turbine which turns in an opposite direction. Thisarrangement has the serious disadvantage that two turbines are necessaryand the reversal of direction of the propellers requires considerabletime so that the maneuverability cf the ship suifers. The smallertnrbine used for reverse operation of the ship lowers the efficiency 0fthe installation because it turns when the ship is being p0wered by theInain turbines. The friction and windage drag of the small turbineconstitutes a power loss and this loss is present whenever the ship isin the ahead direction.

In the turbine-electric system a single turbine is usually arranged todrive a generator of electricity thereby couverting the mechanicalenergy into electrical energy which is then supplied to a motor. Thespeed and direction of the motor, and hence the propeller shaft may thenbe controlled electrically, but the system has the disadvantage that inorder to obtain a high efiiciency an expensive installation is required.

In the case of a diesel engine installation, usually a fixed coupling isused through suitable reduction gears to the propeller shaft. In thisarrangement reversal of direction is accomplished by bringing the engineto a full stop and re-starting it in the opposite direction.Considerable costly mechanism is required for the sole purpose of makingthe engine reversible.

The present invention provides an induction clutch which is a singleunit, and, if designed in accordance With the invention to bereversible, of which the efliciency in the ahead direction does notsulfer to any substantial extent because of its ability to reverse.According to the invention, an induction clutch for transmittingrotative power between two shafts compn'ss a cylindrical shaped stator,a first cylindrical shaped rotor coaxially arranged with respect te thestater and fixed to one of the shafts to rotate therewith, a secondcylindrical shaped rotor coaxially arranged With respect to the statorand fixed to the other of the shafts to rotate therewith, the secondrotor being between the stator and the first rotor, the surface cf thesecond rotor next the first rotor being fitted with windings for directcurrent adapted to establish a predetermined number of alternate northand south magnetic poles, the surface of the first rotor next the secondrotor being fitted with a squirrel cage winding, each of the surfaces cfthe second rotor next the stator and next the first rotor being fittedwith spaced apart parallel conductors, the number of said conductors inthe surface of the second rotor next the stator being N times the numberof said conductors in the surface of the seeond rotor next the firstrotor, where N is a whole number, the surface of the stator next thesecond rotor being fitted with windings for direct eurrent adapted toestablish N times as many alternate north and south magnetic poles as onthe surface of the second rotor next the first rotor, the conductors inthe surface of the second rotor next the stator being directly connectedtogether at one end of the second rotor and said conductors in thesurface cf the second rotor next the first rotor being directly=connected Iogether at the same end cf the second rotor while at theother end of the seconci rotor N Conduetors of like phase in the surfacenext the stator are connected to each of the'conductors in the surfacenext the first rotor.

An induction clutch according to the present invention has the inherentadvantages of electromagnetic coupling between the power unit and thepropeller shaft and is relatively simple and inexpensive. The power unitmay be started, test6d, and warmed up while the sllip is docked, whichcould not be dem: with geared turbine 01' geared diesel engines. Theefiiciency in the ahead direction is high, the only loss being thatrequired for excitation cf the windings. It is satisfactory to have alower efficiency for operation in the astern direction, permitting aninexpensive design for converting mechanical energy into electricalenergy and electrical energy back 1:0 mechanical energy for running theropeller shaft in the reverse direction. lf desired, the clutch can bedesigned for diiferent ratios cf reverse speed to forward speed. Aclutch according to the invention can be adapted for use in anautomobile transrnission because it can be designed to reduce speedwhile increasing torque and to couple and uncouple smoothly.

The invention will be further described with reference to theaccompanying drawings, in which:

Figure 1 is a cross seetional side view of a reversible induetion clutchin accordance with the invention;

Figure 2 is an end view partly in section taken on the line 22 of Figure1;

Figure 3 is an end view partly in section taken on the line 33 of Figure1;

Figure 4 is a cross sectional view cf the central roter of the clutchshown in Figure l, taken 011 the line 4-4;

Figure 5 is an enlarged end view showing part ot die shorting ring onthe central rotor of the clutch shovvn in Figures 1 2 and 3;

Figures 5, 7, 8 and 9 are partial end views showing alter nativearrangements of the wiring et the clutch shown in Figures 1 2 and .3;

Figure 10 is a side view partly in section 0f a reversible clutch inaccordance With the invention arranged 10 previde variable speed;

Figure 11 is a partial end view taken frorn the left band end of theclutch shown in Figure 10; and

Figure 12 is a partial end view taken from Lhe right band end of theclutch shown in Figure 10.

As shown in Figures l, 2 and 3, the reversible induetion clutchcomprises three concentric parts arranged between two aligned ower-transmission shafts 20 and 21. The thr6e concentric parts are an outercylindrical shaped stator 22, a cylindrical shaped rotor 23 arrangedcoaxially with respect to the stator 22, and a cylindrical 'videdbetween the roter 23 amd the bearimg 27. The

shaft 20 is arramged fr rotatiom With respect t0 the stator 22 bypassimg through a ball bearing 29 fixecl to the left hand em d of thestator 22 by anms 30. The roter 24 is fixed to the shaft 21. The clutchis supported cm a base 22a to w'nich the steter 22 is fastemed. Theright hand end of the steter 22 is commected by arms 31 to a ballbearimg 32 through which the straft 21 passes. This arrangememt permitsrotatiom cf the rotors 23 amd 24 relative to ome another amd rotation of00th rotors*23 amd 24 relative to the steter 22. The shaft is driven bythe engime, while the shaft 21 conmects to the pr peller in the case ofthe clutch beimg msed for ship propulsi0m.

In gemeral, the desigm of the various compoments of the reversibleincluction clutch is according to the sarne principles as the design ofthe compomemts 01": conven tiomal electric motors amd gemerators. Theretors 23 amd 24 should be comstructed frorm lamimatedhigh-permieability steel, while the stator 22 cam 'ne censtructecl frormeither lamimated er solid high-perrmeability steel, the choice beimgma.imly a qmestion of ecomormy although laminated construction of thesteter 22, would give beter cperatimg characteristics.

As shown im Figures l, 2 amd 3, the immer surface 'o.f the stator' 22 isfittecl With multiple turn coils 35 cf insulated wire for carryimgdirect cmrremt. Conmeclions (mot sl1owm) are providecl fcr supplyimgdirect curremt to the wimdings 35 so that the directiom of current flowim the Wimdings 35 will poduce alternatrz n-srth amd south poles 0:1 theimmer surface cf the steter 22. Tims, the clesigm er" the steter 22 issnbstamtially the sarne as that cf the steter for a fixed fieldgemerator.

lnsulated lOW resistamce bars 36 are set imtm slots in the eurer surfece0f the roter 23 so that they are parallel to the axis of rotatiom.Amcther set of insulated low re sistamce bars 37 are set into slots imthe immer smrface of the roter 23 amd are also parallel to the axis ofromtiom. In the clutch showm in Figmres l, 2 amd 3 there are twice asmamy bars 56 in the outer snrfece as there are bars 37 in the immersurface of the roter 23. As showm in Figuxe 2, the ends cf all the bars36 at ome amd 0f the rotor 23 are direct-commectecl together by alow-resistamce shortimg rimg 38. A sirnilar shortimg rimg 39 comnectstogether the ends of the bars 37. As shown im Figure 3, imtercommeetinglow-resistamce comcluctors 40 :are provided across the emd of the roter23 opposite t0 the emd shown im Figure 2. The inter-conmec'timgcomductors 40 commect pairs of bars of like phase in the outer surfaceof the roter 23 t0 single bars im the immer surface cf the roter 23.

The immer surface of the roter 23 is fitted with imsulated, multiple-mmfield coils 41, as shown im Figures 1 amd 3. The coils 41 are place-d imslots im the immer surface of the roter 23 amd conmectioms (mot shown)are provided t0 sumply direct curremt to the c0ils 41 to prodmcealtermate north amd soutl1 poles 0m the immer surface of the roter 23.The number of poles produced 0m fithe immer surface of the roter 23 isone-half of the number of poles produced 0m the immer surface cf thestator 22. The design of these coils is similar to that of the fieldcoils of a gemerator. Slip rings (mot shown) of cenvem-tiomal desigmmust be provided for conducting the direct eurremt 10 the field coils ofthe roter 23.

As showm im Figures 4 amd 5, imsulated comductor bars 45 are placed imslots im the outer smrface of the roter 24 amd are imtercomneeted byshort circuit rings 46 at beth emds, ome of the short circuit rings 46beimg showm in Figure 5. lnsulated multiple-Hirn field coils 47 areplaced im slots im the outer surface of the rotor 24. Com

mectioms (mct showm)- are provided t0 conneet the.field seo1ls 47.210. adirect cnrrent seurce so*that the dire'ctiom of cmrrenl. flow willproduce altermate morth amd south poles 0m the outer surface of theroter 24. The number of poles produced 0m the outer surface of the roter24 is the sarne as the murnber of poles produced 0m the immer surface ofthe roter 23. Slip rings (mot shown) cf comvemtiomal design must beprovided f0r comductimg the direct curremt to the fielcl coils 47 of therotor 24. The desigm of the comduetor bars 45 amd their shortimg rings46, which form a squirrel cage, amd of the field coils 47 is similar toIthe design of correspomding parts for a synchromous m1otor.

In operatiom the shaft 20 (Figure l) commects t0 a source of power Whilethe shaft 21 comnects to the part to be drivem, forexarnple, thepropeller shaft 0f a ship. Rotation of the shaft 20 rotates the rotor 23which is fixed to the shaft 20 but which is arramged to rotaterelatively to the shaft 21 by provisiom of the bearings 26 amd 27.Assumimg that the roter 23 is r0tated im a. clocle wise*direction(Figure 3) it will be seen that the rotor 4 can be made to rotateclockwise er anti-clockwise, or remaim statiomary. Accordingly, theclutch, whem used t0 tramsmi't power tothe propeller shaft of a shipachieves the importamt fumctiom of developimg snbstamtially full torqueahead or astern, or m0 torque at all.

With the roter 23 rotated in a clockwise direction by the shaft 20 thewindimgs which are used for forward drive are the Held Wimdimgs 41 0mthe immer -surface of the roter 23, amd the field windings 47 which arein the outer surface of the roter 24. Bach cf these coils is excited bydirect curremt so that am eight-pole magnet is formed aromnd the immersurface of the retor 23.amd around the outer surface of the roter 24.Accordimgly, the roter 24 will follow the roter 23 im symchromism. Thesquirrel cage forrned by the bars 45 (Figures 4 amd 5) in the outersurface 0f the roter 24 serves to start the roter 24 amd .to bring itinto almost symchronous speed with the rotor 23, in the same way as isdome im comvemtional symchromous motors.

In the embodirmemt of the imvention just described the roter 24 haseight poles, the rotor 23 has eight poles 0m the imside amd sixteenpoles 0m the outside, amd the steter 22 has sixteen poles. This sequemce8, 8, 16 amd 16 cam be altered providing the relatiomship 2n, 211,.4namd 4n is maintained. Practical design comsiderations would determimethe value of the integer n.

For operation of the shaft 21 in the reverse direction to that cf thesl1aft 20 the wimdings 35 im the immer surfaces of the stator 22 areexcited oy direct current producing eight north amd eight south poles 0mthe immer surface of the stator 22. Assumimg that the rotor 23 is 'beimgdriven by the shaft 20 at 500 R. P. M. in the clockwise direction, thecomductors 36 im the outer surface of the roter 23 Will have amalternatimg voltage 01 4,000 cycles per rnimute gemerated im them amdWill produce alternating curremt cf 4,000 cycles per mimutefrequemcy.The conductors 40 (Figure 3) across ithe-emd 'of the roter 23 carry this4000 per mimute current to the conductors' 37 0m the immer surface ofthe roten 23.

Thus the stator 22 amd theouter portiom of the roter 23 fumccion as al6-pole 3-phase gemerator. The comdnctors 37 0m the immer surface of theroter 23 areessemtially the wimdings of an 8-pole 3-phase motor, themurmber of poles on the immer surface of a rotor 23 being onehalf thenumber of the outer surface because of the 2 to 1 imterconmectiom acrossthe emd of the roter 23 by the conductors 40.

The 3-phase curremt at 4,000 eycles per mimmte in the conductors 37 imthe immer surface of the roter 23 excite a field 0f 4 north amd 4 southpoles which rotates relative to the roter 23 at 1,000 R. P. M. in acounterclockwise directiom. Because the roter 23 rotates a-t 500 R.P. M.clockwise, the field of an immer snrface of the roter. 23 rotatesrelative to a fixed object at 500 R. P. M. ..counterclockwise. This 500R. P; M.counterclockwiserotatimg field will induce curremt in thesquirrel cage comductors 45 (Fignres 4 and 5) of the rotor 24 causingthe rotor 24 to accelerate counterclockwise until a speed slightly lessthan 500 R. P. M. is attained. If desired, the coils 47 of the rotor 24may be excited by direct current producing poles 011 the unter surfaceof the rotor 24 which Will lock with the rotating field 0n the immersurface of the rotor 23 and drive the rotor 24 and its shaft 21 at 500R. P. M. cnunterclockwise. Accordingly it can be seen rhat, with therotor 23 driven by the shaft 20 at any given speed, exciting field coilscf the stator 22 Will cause the rotor 24 and its shaft 21 to rotate inthe direction opposite to that in which the shaft 20 is driven. Therotor 24 and its shaft 21 may be operated at a speed slightly less thanthat er": the shaft 20 and the rotor 23 when the coils 47 of the rotor24 are not excited, or the shaft 21 may be driven a1: the same speed asthe sha.ft 20 by exciting the field coils 47 of the rotor 24. It is tobe noted that field coils in the rotor 24 are essential only inapplications requiring synchronous speed. Where this is not required thecost cf the machine may be reduced by -eliminating the field coils fromthe rotor 24.

In the embodiment of -the reversible induction clutch shown in Figures 1to 5, three conductors in the outer and inner surfaces of the rotor 23,have been used for each pair of poles so that the machine contains theelements of a 3-phase generator and a 3-phase motor. The choice of threephases is an arbitrary one and not an essential feature of the machine.Another number of phases may be used, the optimum number being indicatedby practical design considerations. The design of the individualcomponents of the reversible induction cluteh can be carried out bythose skilled in the art 0f designing generators and motors. Thedesigner would deeide the number of poles in the stator, the nurnber ofphases, the thickness of the rotor 23 having regard for the adverseeifeet of that magnetic flux on the outer snrface might have on the fluxon the inner surface. The clutch might be designed With the rotor 24placed outside and the stator 22 placed inside of the rotor 23.

An alternative design of the reversible induction clutch is illustratedby Figure 6. The general strueture of this alternative is the sarne asthat shown in Figures 1 to 5, so rhat only variations in the design willbe discussed below.

Figure 6 shows a sector of an end view such as that shown in Figure 3.The unter part is a stator 50 surrounding concentric rotors 51 and 52.The rotor 52 is fixed to a shaft 53. The rotor 52 is driven by the shaft53 from the power unit and turns it in one direction only. The rotor51is eonnected to the driven shaft, which is to be driven in eitherdirection. The rotors 51 and 52 are cf the same construction as therotors 23 and 24 shown in Figures 1 2 and 3. The stator 50 has fieldwindings 54 which correspond to the field windings 35 of the stator 22shown in Figures 1, 2 and 3. In addition, the stator 50 has a set ofbars 55 which are short circuited by rings 56 at each end 0f the stator50, forming a squirrel sage similar to that used in induction motors.

In operation the rotor 51 can be driven in either direction. T0 stattthe rotor 51 turning in a direction opposite to that of the rotor 52 thefield Windings 57 in the rotor 52 are excited to produce 8 poles, 4north and 4 south 011 the outer surface of the rotor 52. As before, itis assumed that the rotor 52 is being retated a-t 500 R. P. M.cleekwise. While the rotor 51 is at rest all the conductors on its innersurface Will be cut by the rotating field of the rotor 52 and Will havealternating voltage of 4 500=2,000 cycles per minute generated in them,and will 'produce alternating current of 2,000 cycles per minute. Theconductors 58 across the end of the rotor 51 carry the 3-phase, 2,000cycles current to the conduetors in the unter surface ef the rotor 51and this current Will excite on the outer surface 0f the rotor 51, 8north and 8 south poles which Will rotate at 2000/8=250 R. P. M.clockwise. The fiur of these poles cuts the squirrel cage bars 55 of thestator 50 and because of the induced current in the bars 55 a force isexerted by the field on the stator 50 tending to turn it in a clockwisedirection. I-Iowever, the stator 50 is fixed and cannot rotate so thatthe stator 50 produces a reaction in a counter clockwise directionacting on the rotor 51 to accelerate it in a counterclockwise direction.As soon as the rotor 51 is in motion the frequency of the current is nolonger 2,000 cycles per minute. For example, if the rotor 51 turns at R.P. M. counterclockwise the relative speed cf the rotor 51 to the rotor52 is 100+500=600 R. P. M. Hence, the frequency of eurrent in the rotor51 is 600 4=2400 cycles per minute. The field an the outer surface ofthe rotor 51 will then rotate relative to the rotor 51 at 2,400/8=300 R.P. M. which is a rotation relative to the stator 50 of 300-100=200 R. P.M.

As the speed cf the rotor 51 increases, the speed of the field cuttingthe bars 55 of the stator 50 decreases and would be stationary if therotor 51 could turn at 500 R. P. M. However, the rotor 51 cannot attainthis speed by induetion but can approach it, and when the rotor 51 isturm'ng at slightly less than 500 R. P. M. the field coils 54 of thestator 50 may be energized thereby synchronizing the speeds of therotors 51 and 52. Under these conditions the rotor 52 turns clockwise at500 R. P. M. and causes the rotor 51 to rotate counterclockwise at 500R. P. M.

The rotor 51 can be caused to rotate in the same direction as the rotor52 by energizing the field coils 59 cf: the rotor 51. The bars -of thesquirrel eage cf the rotor 52 tl1en have current induced in thern whichwill force the rotor 51 to turn in the same direction as the rotor 52.When the speed of the rotor 51 becornes slightly less than that 01 therotor 52 the field coils 57 in the rotor 52 may be energized tosynchronize the rotors 51 and 52.

The alternative design shown in Figure 7 is the same as that shown inFigure 6 except that there are three times as many bars in the outersurface of the rotor 51 as in the inner surface .of this rotor and, inthe case of the stator 50, the nurnber 0f: field coils 54 is changed toproduce three times as many poles as there are 011 the unter snrface ofthe rotor 52. The opera=tion of this clutch design can be understood byfollowing the sarne reasoning as described above in connection withoperation of the construction shown in Figure 6. The rotor 51 may beeaused to rotate at the same speed and in the same direction as therotor 52 or in the reverse direction at one-half the speed cf the rotor52.

Other alternatives are possible with M times as many bars in the outersurfaee of the rotor 51 as in the immer surface, and M times as manybars 011 the stator 50 as on the rotor 52. With the rotor 52 rotating inone direction, the rotor 51 may be eaused to rotate at the same speed inthe same direction or in the reverse direction at times the speed of therotor 52. It is -to be noted that field coils in the stator 50 areessential only in applications requiring synchronous speed f0r thereverse direction. Where this is not required the cost cf the machinernay be reduced by eliminating the field coils from the stator 50.

A variable speed non-reversing elutch is shown in Fig ure 8 in which allarts are the same as those shown in Figure 6 except that the connections70 across the end of the rotor 51 are crossed with respect to the endconnections 58 of Figure 6. As before, the rotor 52 is connected by ashaft 53 to the power unit so that it is turned in one direction only.The rotor 51 is cormected to the shaft which is required to be at rest,turned at the same speed as the rotor 52, or turned at a rednced speedand with increased torque.

In the construction shown in Figure 8, when the field coils 57 of therotor 52 are excited, the rotor 51 will turn' in the same direction asthe rotor 52 but at a speed which approaehes one-third of the speed ofthe rotor 52. Assuming the rotor 52 rotates at 500 R. P. M. clockwiseand the rotor 51 is stationary, them the flux of the four north and foursouth poles on the rotor 52 cutting the conductors in the immer surfaceof the rotor 51, Will gemerate im the conductors altermating current ata frequemcy of 4 500=2000 cycles per mimute. The current carried acrossthe end of the rotor 51 to conductors im the outside surface 015 therotor 51 will excite 8 north and 8 soutn poles rotating at 2,000/ 8:250R. P. M. As the end comnections 70 are crossed with respect t those cfFigure 6, the sequemce is reversed and the field rotation is counterclockwise This rotating field will induce curremt in the squirrel cage ofthe stator 50 and hence exert a counterclockwise turnimg eflort 011 thestator 50. Because the stator 50 is fixed and cannot rotate the reactioncf this turning force on the stator 50 is a clockwise turning forceactimg on the rotor 51 which will give the rotor 51 a clockwiseacceleration. When the rotor 51 is in motion the frequency is m0 longer2,000 cycles per mimute. F01 example, if the rotor 51 turns at 100 R. P.M. clockwise the speed of the rotor 52 relative to the rotor 51 is500100=400 R. P. M. The frequency of the current is then 4 400=1600cycles per minute. The field on the outside of the rotor 51 rotatesrelative to the rotor 51 at 1600/8=200 R. P. M. counterclockwise. Thisfield rotates at 200100=100 R. P. M. counterclockwise relative to thestator 50. As the speed of the rotor 51 increases, the speed of thefield cutting the squirrel cage bars in the stator 50 decreases andwould be stationary if the rotor 51 could turn at 166% R. P. M. However,the rotor 51 cannot attain this speed by imduction but can approach it,and when the rotor 51 is turning at slightly less than 166% R. P. M. thefield coils im the stator 50 may be emergized thus synchronizing therotors 51 and 52. Umder these conditions the rotor 52 turns clockwise at500 R. P. M. and the rotor 51 turms clockwise at 166% R. P. M. T0 causethe rotor 51 to turn at the same speed and in the same direction as therotor 52 the field coils of the rotor 51 are emergized. By induction therotor 51 will turn at slightly less than the speed cf the rotor 52 andmay be synchronized by exciting field coils in the rotor 52.

Another design 0f a variable speed clutch is illustrated in Figu.re 9and the parts showm are the same es those showm im Figure 7 except forthe rotor 51 which has diflerer1t cross comnections 80 as shown inFigure 9. The reasoning behind the Operation of the variable speedclutch shown in Figure 9 is similar to that described above inconnectiom With the variable speed clutch sh-owm in Figure 8. The rotor51 of the clutch shown im Figure 9 may be made to rotate in the samedirection as the rotor 52 and at the sarne speed or at ome-fourth cf thespeed of the rotor 52.

Other variable speed clutches similar im principle to those described incomnectiom with Figures 8 and 9 may be designecl. With M times as manybars in the outer surface of the rotor 51 as in the immer surface and Mtirnes as many poles 011 the stator 50 as 0m the rotor 52, the rotor 51may be caused to rotate in the sarne direction as the rotor 52 at thesame speed 01' at of the -speed of the rotor 52.

A construction of a variable-speed reversible clutch is illustrated byFigures 10, 11 and 12. T he various components are the same as in Figure8 and for the sake of clarity in Figures 10, 11 and 12, omly the rotor85 which runs betweem the stator and the central rotor is shown, and thefield W111d111g5 are omitted. The roter 85 has an immer and an outer setof conductors 86 and 87 which are interconnected at each emd of therotor85 by interconmections 88 and 89. Each interconnectiom 88 0r S? hasa projectimggcontact 90 or 91. Two short-circuit rings92 amd93,

one at each end of the rotor 85, are arranged by any comvenient means(not shown) so tl1at they may be moved parallel to the axis of the rotorinto and out of contact with the comtacts and 91.

In operatiom, when the rimg 92 is moved to short-circuit the comtacts90, the cross-conmectioms 88 on that end of the roter 85 areshort-circuited and crosswonnections 39 are etrective, and the clmtchoperates im the same way as that shown in Figure 6. When the ring 92 ismoved away from the contacts 90, and the rimg 93 is moved toshortci1cuit the comtacts 91, the cross-commectioms 89 areshortcircuited and cross-comnectioms 88 are effective, and the clutchoperates in the same way as that shown in Figure 8. Accordingly, therotor 85 may be (l) coupled directly to the cemtral rotor 52 (seeFigures 6 and 8), (2) driven in the same direction as the rotor 52 atome-third of the speed cf the rotor S2, er (3) drivem im the reversedirecden at full speed.

An alternative construetion womld be to have one end of the rotor 85cross connected as im Figure 7 and the other end as im Figure 9 withcontacts and movable rings as im Figure 10. Then the rotor 85 may be (l)couplecl direct to the rotor 52 (see Figures 7 and 9), (2) driven in thesame direction as the rotor 52 at ome-quarter the speed, er (3) drivenin the reverse direction at one-half speed.

Other variable-speed reversible clutches rnay be desigmed. The endcross-comnections and the movable rings would be as shown in Figures 10,11 and 12, but with M times as rnamy conductors in the outer surface asin the immer surface of the rotor 85, and also M tirnes as many poles imthe stator 50 (Figures 6 and 8) as im the rotor 52.

Then, the rotor 85 may be 1) coupled direct to the rotor 52, (2) drivenin the same direction as the rotor 52 at of the speed 0f the rotor 52,01' (3) driven im the reverse directiom at of the speed of the rotor 52.

What I claim as rny imventirm is:

1. Am imductiom clutch for transmitting rotative ower betweem two shaftscomprisimg, a cylindrical shaped stator, a first cylindrical shapedrotor coaxially arranged with respect to the stator and fixed to one ofsaid shafts to rotate therewitl1, a secomd cylimdrical shaped rotorcoaxially arramged with respect to the stator and fixed to the other ofsaid shafts to rotate therewith, the second rotor being betweem thestator and the first rotor, the surface of the second rotor next thefirst rotor being fitted With windings for direct current adapted toestablish a predetermined number of alternate north and south magneticpoles, the surface cf the first rotor next the second rotor being fittedWith a squirrel eage windimg, each of the surfaces of the second rotormext the stator and next the first rotor being fitted With spaced apartparallel conductors, the number 015 said conductors im the surface ofthe seconcl rotor next the stator being N times the mumber of saidcomductors in the surface of the second rotor next the first rotor,where N is a whole murnber, the surface of the steter mext the secomdrotor being fitted With windings for direct curremt adapted to establishN times es many alternate north and south magnetic poles as 011 thesurface of the second rotor next the first rotor, said conductors im thesurface of the second rotor next the stator being direct connectedtogether at one end 0f the second rotor and said comductors in thesurface of the secemd rotor mext the first rotor being direct connectedtogether at the sarne end 01? the second rotor while at the other end ofthe second rotor N conductors of like phase in the surface next thestator are connected t0 each of the .comductors in the surface next thefirst rotor.

2. An induction clutch as defined im claim .1 in which the spaced apartparallel conductors im each of the surfaees cf the second rotor areuniformly spaced apart and are fixed parallel to the axis of rotation ofthe second roter.

3. An induction clutch as defined in claim 2 in which the surface of thefirst roter next the second roter is fitted with windings for directcurrent adapted to establish a predeterrnined number of alternate northand south poles.

4. An induction clutch as defined in claim 3 in which the whole number Nis two.

5. An induction clutch as defined in claim 1 in which the surface of thefirst rotor next the second roter is fitted with windings for directcurrent adapted to establish a predetermined number of alternate northand south poles.

6. An induction clutch as defined in claim 5 in which the whole number Nis two.

7. An induction clutch as defined in claim 1 comprising, a squirrel cageWinding fitted into the surface of the stator next the second roter.

8. An induction clutch as defined in claim 7 in which the spaced apartparallel conductors in each of the surfaces of the second roter areuniformly spaced apart and are fixed parallel to the axis of rotation ofthe second roter.

9. An induction clutch as defined in claim 8 in which the surface of thefirst roter next the second rotor is fitted With Windings for directcurrent adapted to establish a predeterrnined number of alternate northand south poles.

10. An induction clutch as defined in claim 9 in which the whole numberN is two.

11. An induction elutch as defined in claim 1 comprising, a squirrelcage winding fitted into the surface of the stator next the secondroter, and in which the whole number N is three.

12. An induction clutch as defined in claim 11 in which the spaced apartparallel conductors in each of the surfaces of the second rotor areuniformly spaced apart and are fixed parallel to the axis of rotation ofthe second rotor.

13. An induction clutch as defined in claim 12 in whicl1 the surface ofthe first roter next the second roter is fitted with Windings for directcurrent adapted to establish a predetermined nurnber of alternate northand south poles.

14. An induction elutch for transmitting rotative power between twoshafts comprising, a cylindrical shaped stator,

a first cylindrical shaped roter coaxially arranged with respect to thestator and fixed to one of said shafts to rotate therewith, a secondcylindrical shaped roter eo axially arranged with respect to the statorand fixed to the other of said shafts to rotate therewith, the secondroter being between the stator and the first roter, the surface of thesecond rotor next the first roter being fitted with windings for directcurrent adapted to establish a predetermined number of alternate northand south magnetic poles, the surface of the first rotor next the seccndrotor being fitted with a squirrel cage winding, each of the surfaces ofthe second roter next the stator and next the first roter being fittedwith spaced apart parallel conduct0rs, the number cf said conductors inthe surface of the second roter next the stator being N times the numberof said conductors in the surface of the seeond rotor next the firstroter, where N is a whole nurnber, the surface of the stator next thesecond roter being fitted with a squirrel cage winding and with windingsfor direct current adapted to establish N times as many alter nate northand south magnetic poles as an the surface cf the second roter next thefirst rotor, interconnections at each end of the seconcl roter fro;n Nconductors of like phase in the surface of the second roter next thestator to each of the conductors in the surface of the second roter nextthe first roter, said interconnections at one end cf the second rotorbeing crossed with respect to said interconnections at the other end,and means operable to short circuit the said interconnections at eitherend of the second roter.

15. An induction clutch as defined in claim 14 in which the spaced apartparallel conductors in each of the surfaces ofthe second rotor areuniformly spaced apart and are fixed parallel to the axis of rotation ofthe second rotor.

16. An induction elutch as defined in claim 15 in which the surface ofthe first roter next to the second roter is fitted with windings fordirect current adapted to establish a precletermined number of alternatenorth and south poles.

17. An induction clutch as defined in claim 16 in which the whole numberN is two.

18. An induetion clutch as defined in claim 14 in which the whole numberN is two.

N0 references cited.

